The present invention relates to the production of darkening and protection devices for windows or doors, e.g. curtains or mosquito nets, these curtains or nets rolling and unrolling on a cylinder structure.
In particular, the present invention relates to a mechanism for locking the curtains or mosquito nets in a desired position, usually open or closed, but mainly in any intermediate position.
Devices have heretofore been provided, as including a roll, on which the curtain or mosquito net rolls up, supported by suitable, substantially horizontal means.
This roll is usually introduced in a suitable case situated over, or in any case, near the upper edge of the window or door.
The free end of the curtain goes out of said case through a relative slot.
The curtain can be operated by a suitable drive member, basically including a pulley, which is integral with the roll and is connected to a relative, generally endless pull rope going out of the case at the sides of the pulley.
The roll is driven into rotation in the rolling direction by pulling down one of the rope ends, whereas it is driven into rotation in the unrolling direction by pulling down the other of the rope ends.
Suitable locking means, usually connected to the roll, allow the curtain to be firmly positioned, approximately in the desired point.
The main disadvantage of these locking mechanisms derives from the fact that they are not sufficiently resistant, when the curtain moves, either in rolling or unrolling direction.
These locking mechanisms must offer a sufficient resistance when the curtain is motionless, so as to maintain it in the predetermined position, overcoming possible action of elastic means connected to the roll, which would tend to roll it.
This locking mechanism can be formed by brakes, which elastically interfere with a support fastened to the roll on which the curtain is positioned.
The dimension of the brakes, wound around a suitable blocking part, prevents roll free rotation, if the curtain is not stressed from outside.
Other devices have been proposed, as shown in FIG. 1, in which the curtain control means C feature a hollow roll B, coaxial therewith, which has, made therealong, a slit B1 cooperating with the ends D1, D2 of a plurality of elastic means D, freely wound around an inner roller A, stationary and coaxial with the hollow roll B.
When suitable transmission means drive the control means C to rotate, the edges of the slit B1 go in abutment against the ends D1, D2 of the elastic means D, thus twisting them.
When one of the edges of the slit B1 strikes the related end D1 or D2 respectively, the friction of the elastic means D, wound around the inner roller A and sliding therealong, is reduced, thus facilitating the curtain rolling and unrolling.
If the control means C are not operated by the user, the action of the elastic means D on the inner cylinder A determines a friction against mutual sliding, and the friction action is bigger than the weight action of the portion of the curtain not wound around the hollow roll B.
The above mentioned technical solutions are worldwide marketed, yet they have a very big drawback resulting from a considerable unreliability of the curtain positioning.
This unreliability is a direct consequence of the difference between the circumference arc corresponding to the transversal dimension of the slit B1 and the distance between the ends D1, D2 of the elastic means D; this is a problem particularly in case of mosquito nets.
Moreover, the more stressed components, in particular the edges of the slit B1 of the hollow roll B and the ends D1, D2 of the elastic means D, lack structural resistance.
If the locking mechanism maintenance, which is very expensive, is not proper, a structural deficiency of the hollow roll B in the slit B1 area can seriously jeopardize the locking mechanism functionality, thus damaging its reliability.
Moreover, it is to be pointed out that the described technical solutions are obtained by using very expensive components and specialized manpower.
In fact, the cost of this mechanism depends on its dimension, which is related to the curtain dimensions.
Further, it is necessary to prepare a wide range of sizes for satisfying the market different needs.
This invention was evolved with the general object of avoiding the above mentioned drawbacks by proposing a mechanism for locking curtains and the like which guarantees a rapid, precise and stable locking in any position and in any angular position of the curtain supporting roll.
Another object of the present invention is to propose a locking mechanism, which is particularly strong and reliable in different working conditions.
A further object of the present invention is to propose a considerably versatile locking mechanism, which has almost the same size for curtains and nets of different dimensions.
Yet another object is to propose a locking mechanism obtained by a simple technical solution, which guarantees correct rolling and unrolling and which is extremely functional, reliable and cheap.
The above mentioned objects are obtained, in accordance with the contents of claims, in a mechanism for locking curtains and the like including a sleeve rotating about a longitudinal axis and fastened to a roll, in coaxial relation therewith, with a curtain or a similar article rolled up on said roll, said mechanism being fastened to a stationary support structure, by providing said mechanism with:
a barrel which enters freely said sleeve and couples firmly with said structure by relative coupling means, with said barrel featuring, made therein, at least one radial housing opening outside of said barrel;
at least one elastic element introduced freely in this radial housing and co-operating with friction means, said friction means being kept in contact with an inner surface of said sleeve due to the action of these friction means on the elastic element.
According to a different embodiment of the invention, the mechanism includes:
a barrel which enters freely said sleeve and couples firmly with said structure by relative coupling means;
a plurality of series of radial housings made in said barrel, with housings of each series all aligned and opening outside of said barrel, with corresponding axes of said housings being laid in a relative longitudinal plan passing through a longitudinal axis of this barrel;
at least one elastic element introduced freely in each radial housing and co-operating with relative friction means, said friction means being kept in contact with an inner surface of said sleeve due to the action of these friction means on the elastic element.